We learned previously (daf 39) that a number of miracles took place in the Temple during the time that Shimon HaTzaddik was serving as the kohen gadol. One of them was that the lottery always ended up with the animal that was to be sacrificed to God coming up in his right hand.
A baraita teaches: Rabbi Akiva’s students asked him: If the lot for God was drawn by the High Priest’s left hand, what is the halakha with regard to whether he may transfer the lot to his right hand? He said to them: Do not give the Sadducees an opportunity to dominate. If it is allowed, they will adduce this as proof of their claim that the halakhot are not absolute, and the Sages have the power to change them as they see fit.
During the latter part of the second Temple period there were sects of Jews who strayed from the traditional path of the Sages on one level or another. Among these “minim” were the early Christians, but mainly it was a variety of Gnostic sects. While there were major differences between the groups, all of them were similar in their rejection of the tradition as it was taught by the Sages. Among their accusations against the Sages was the claim that the Sages did not truly follow the Torah properly.
The simple meaning of Rabbi Akiva’s statement was that he wanted to defend the Sages from the accusation that they did as they chose. Rabbenu Hananel explains that if the lottery always turned up in the kohen gadol’s right hand, this may – in their minds – offer support to those sects who believed that there was two powers ruling the world, God and Azazel. Were the lottery to always appear in the kohen gadol’s right hand, that would show the supremacy of God over His “rival” – Azazel. Since it sometimes came up in the left hand, their “proof” was destroyed.
The Meiri’s explanation is that the minim would argue that the Sages were engaged in witchcraft and magic, were the lottery always to appear in the kohen gadol’s right hand, so it was important that it should be presented honestly.